High-Temperature Bioethanol Fermentation by Conventional and Nonconventional Yeasts

Abstract

Fuel ethanol production has dramatically increased in the world. Ethanol fermentation for alcohol beverage is a traditional and mature technology. However, the fermentation technology for fuel ethanol should be reconsidered because it must be large scale and low cost. High-temperature fermentation is the most promising approach for efficient fuel ethanol production from the viewpoints of cost reduction and robustness. In addition, high temperature makes it possible to establish simultaneous saccharification and fermentation process because enzyme activities can be enhanced. For the high-temperature fermentation, thermotolerant ethanol-producing yeasts are necessary. In this chapter, yeast strains suitable for high-temperature bioethanol fermentation are reviewed. Among these, Kluyveromyces marxianus achieved sufficient ethanol production in a pilot-scale high-temperature fermentation from starch contained in waste cassava pulp. Studies of the thermotolerant mechanisms will help to construct genetically engineered yeasts for further cost-effective high-temperature ethanol fermentation.